From 938e28acafd0ead223b021caf5880ee63f3a7f33 Mon Sep 17 00:00:00 2001
From: JupiterRider <60042618+JupiterRider@users.noreply.github.com>
Date: Sat, 8 Apr 2023 13:05:19 +0200
Subject: [PATCH 1/2] Add IupMenu OPEN_CB callback

---
 iup/bind_callbacks.go | 35 +++++++++++++++++++++++++++++++++++
 iup/bind_events.go    |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/iup/bind_callbacks.go b/iup/bind_callbacks.go
index 898e102..c6b4ccd 100644
--- a/iup/bind_callbacks.go
+++ b/iup/bind_callbacks.go
@@ -389,6 +389,11 @@ extern int goIupMultiUnselectionCB(void *ih, int* ids, int n);
 static void goIupSetMultiUnselectionFunc(Ihandle *ih) {
 	IupSetCallback(ih, "MULTIUNSELECTION_CB", (Icallback) goIupMultiUnselectionCB);
 }
+
+extern int goIupMenuOpenCB(void *);
+static void goIupSetMenuOpenFunc(Ihandle *ih) {
+	IupSetCallback(ih, "OPEN_CB", (Icallback) goIupMenuOpenCB);
+}
 */
 import "C"
 
@@ -2570,3 +2575,33 @@ func setMultiUnselectionFunc(ih Ihandle, f MultiUnselectionFunc) {
 }
 
 //--------------------
+
+// MenuOpenFunc for OPEN_CB callback.
+// Called just before the menu is opened.
+//
+// https://www.tecgraf.puc-rio.br/iup/en/call/iup_open_cb.html
+type MenuOpenFunc func(ih Ihandle) int
+
+//export goIupMenuOpenCB
+func goIupMenuOpenCB(ih unsafe.Pointer) C.int {
+	uuid := GetAttribute((Ihandle)(ih), "UUID")
+	h, ok := callbacks.Load("OPEN_CB_" + uuid)
+	if !ok {
+		panic("cannot load callback " + "OPEN_CB_" + uuid)
+	}
+
+	ch := h.(cgo.Handle)
+	f := ch.Value().(ActionFunc)
+
+	return C.int(f((Ihandle)(ih)))
+}
+
+// setMenuOpenFunc for OPEN_CB.
+func setMenuOpenFunc(ih Ihandle, f MenuOpenFunc) {
+	ch := cgo.NewHandle(f)
+	callbacks.Store("OPEN_CB_"+ih.GetAttribute("UUID"), ch)
+
+	C.goIupSetMenuOpenFunc(ih.ptr())
+}
+
+//--------------------
diff --git a/iup/bind_events.go b/iup/bind_events.go
index 6749bb9..0aede0c 100644
--- a/iup/bind_events.go
+++ b/iup/bind_events.go
@@ -258,6 +258,8 @@ func SetCallback(ih Ihandle, name string, fn interface{}) {
 		setMultiSelectionFunc(ih, fn.(MultiSelectionFunc))
 	case "MULTIUNSELECTION_CB":
 		setMultiUnselectionFunc(ih, fn.(MultiUnselectionFunc))
+	case "OPEN_CB":
+		setMenuOpenFunc(ih, fn.(MenuOpenFunc))
 	}
 }
 

From 49c1a7d4035f76778d28944f5ad2951b9332d5f8 Mon Sep 17 00:00:00 2001
From: JupiterRider <60042618+JupiterRider@users.noreply.github.com>
Date: Sat, 8 Apr 2023 13:41:23 +0200
Subject: [PATCH 2/2] Fix wrong type assertion

---
 iup/bind_callbacks.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/iup/bind_callbacks.go b/iup/bind_callbacks.go
index c6b4ccd..3c11dc2 100644
--- a/iup/bind_callbacks.go
+++ b/iup/bind_callbacks.go
@@ -2591,7 +2591,7 @@ func goIupMenuOpenCB(ih unsafe.Pointer) C.int {
 	}
 
 	ch := h.(cgo.Handle)
-	f := ch.Value().(ActionFunc)
+	f := ch.Value().(MenuOpenFunc)
 
 	return C.int(f((Ihandle)(ih)))
 }